Discharge device



March 29, 1960 A w, w o 2,930,919

DISCHARGE DEVICE Y Filed Jan. 15, 1959 FIG; I

FIG. 3.

INVENTOR.

ALBERT w. wAlmo.

United States PatentC DISCHARGE DEVICE Application January 15, 1959, Serial No. 786,993 '4 Claims. (Cl. 313-109) This invention relates to radiation-generating discharge devices and, more particularly, to low-pressure, mercuryvapor discharge devices intended to be operated under conditions of relativelyhigh loading.

vIt is well known that the standard fluorescent lamp operates with the highest lumen perwatt efiiciency when the mercury-vapor pressure within the lamp is from about 6 to 9 microns. A mercury-vapor pressure within this range is readily obtained by having a region within the lamp where condensed mercury is at a temperature of from about 40 C. to 45 C. With the standard fluorescent lamp, this condition is readily obtained withoutdifficulty. Where fluorescent lamps are operated with greater power input without auxiliary arrangements for controlling the mercury-vapor pressure, the higher power input per unit volume of the lamp envelope will result in in creased mercury-vapor pressure, thereby decreasing .the

effieiency of the lamp. As an example, the usual fluorescent lamp operates with a loading of about 10 watts per foot of lamp envelope length. Higher-loaded lamps can operate with a loading of about 25 watts per foot of envelope length and the degree of increased loading can be varied considerably. In order to decrease the operating mercury vapor pressure within so-called high-loaded fluorescent lamps and thereby at least approach a maximum of efficiency in generating ultraviolet radiations, it has been proposed to use heat-deflecting shields proximate the ends of the envelope in order to form cooling chambers. The minimum temperature within the cooling chambers establishes the mercury-vapor pressurewithin the dischargedevice. The use of the higher loadings in conjunction with such heat shields has introduced additional problems, however, in that the maintenance of light emission or output is impaired. In other words, as the lamp .is operated the curve of light output versus hours opera tion drops off faster than with a conventional fluorescent lamp.

It is the general object of this invention to avoid and overcome the foregoing and other difiiculties of and objections to prior-art practices by the provision of a discharge device which is adapted to be operated with higher loadings and which has improved maintenance of light output.

It is another object to provide improved heat shields for so-called, high-loaded fluorescent lamps in order to improve the maintenance of light output for such lamps. yltis a further object to provide improved lead eonductorsand anodes for high-loaded fluorescent lamps to supplement the improved heat shields, in order further to improve the maintenance of light output for such lamps. v y The aforesaid objects of the invention, and other objects which-will become apparent as the description proceeds, are achieved by providing-a specific black chrome- .vanadium plating on the heat shields of the lamp. -In addition, .the enlarged. anodes and-lead conductors which are used with theJam -are also desirab ly provided with the black chrome-vanadium plating.

For a better understanding of the invention, reference i should be had to the accompanying drawing wherein:

Fig. l is an elevational view, partly in section, of a highload fluorescent lamp wherein the heat shields, anodes, and lead conductors carry a specific black chrome-vanadium plating in accordance with this invention;

Fig. 2 is a sectional view taken on the line II--1II in Fig. 1 in the direction of the arrows;

Fig. 3 is a perspective view of a portion of a mount for the lamp as shown in Fig. 1, further illustrating the plated heat shield, lead conductors and enlarged anodes.

With specific reference to the form of the invention i1- lustrated in the drawing, the lamp 111 in Fig. 1 comprises a generally-tubular envelope 12 which carries a phosphor coating 14 on the interior surfaces thereof. The envelope encloses an inert, ionizable starting gas such as argon at a pressure of 4 mm. and a small charge of mercury 16. Sealed intoeither end of the envelope 12 is a mount 18 which comprises an elongated, vitreous, reentrant stem 20 having lead conductors 22 sealed through the press portion thereof. A conventional Dumet wire section is used in the lead conductors to facilitate making a good hermetic seal as is customary and the inwardly extending lead conductor portions can be fabricated ofnickel, iron or nickel-iron alloy for example. Oxide-coated electrodes 24 are supported between the inwardly-extending extremities of the lead conductors 22. As is usual, the electrodes 24 are operatively disposed at either end of the envelope 12 and are adapted to support a positive-column discharge therebetween. In order to prevent overheating of the portions of the lead conductors 22 which are proximate the electrodes 24, enlargedanodes 26'are electrically connected to each of the lead conductors 22 and in their illustrated preferred form, these enlarged anodes 26 are provided with an L configuration with the longest anode dimension paralleling the electrodes 24.

Metallic heat shields 28 are afiixed to the press portions 30 of each stem 20 proximate each end of the envelope 12 and closer to the ends of the envelope than the electrodes 24. The size of each of the heat shields 28 is such that a gas passage is maintained between the shields 28 and the inner surface of the lamp envelope 12. Alternatively, aperturescan be provided through each of the heat shields 28 to permit the passage of gas. Cooling chambers 32 are thus formed between the ends of the enelope 12 and each of the heat shields 28. These cooling chambers 32 establish the operating mercury-vapor pressure within the lamp 111 since the maximum mercury-vapor pressure is governed by the coolest location within the designed to operate with a power input 'of 25 watts per foo-t of envelope length and the envelope 12 can have an overall length of 4 feet and an outer diameter of 1% inches. The coils which form part of the electrode '24 can be formed of coiled-coil tungsten wire, the inner coil of which is filled with a conventional mixture of alkalineearth oxides. The phosphor coating 14 is conventional and can comprise a usual halophosphate-type phosphor or zinc-silicate, activated by manganese for example. The L-shaped enlarged anodes 26 have a long dimension of /8 inch, a short dimension of inch and a width of inch and are affixed to thelead conductors 22 with asiniple spot weld. The starting gas which is contained within the envelope isa'rgon as noted and other noble 'gases'or Patented Mar. 29, 1961) mixturesthereo'f at varying pressures can be substituted therefor. In the preferred form, each of the heat shields 28 is generally-circular in configuration with a maximum diameter of 1 inch. The heat shields and enlarged anodescanibeformed'of nickel, iron or nickel iron alloy for example from to 1'3 mil 'sheet stock. As'noted hereinbefore, the heat shieldsZS aredesirably aflixed to the press '30 of each stem 20. This is conveniently accomplished by providing aretainingslot in'the center section of eachshield '28'and'ben'ding the formed tab-like center section 34 of each heat shield intoelectrical continuity with one of .the lead conductors 22. 'For the foregoing specific example, the distance from each heat shield 28 to the closest electrode 24 is approximately inch and each of the cooling chambers 32 which are'formed have a maximumlength of approximately 2 inches. It should be understood that the foregoing preferred design is subject to considerable variation. For example, the enlarged anodes 26 can vary in size and canine provided with other configurations such as circular or rectangular. Also, the heat shields 28 can be afiixed directly to one of the lead conductors 22 rather than the press 30, electrically insulating the shields from the other of the lead conductors, and the size of the formed cooling chambers 32 can be varied considerably.

In accordance with the present invention, at least the heat shields 28 are provided with a black chrome-vanadium plating or coating 36. A plating of this nature is disclosed in copending application S.N. 591,206, filed June 13, 1956 by Wainio'and Sutter and owned by the present assignee, now US. Patent No.2,'885,587, dated May '5, 1959,the first-named inventor being the inventor herein. A similar plating is also disclosed in US. Patent 'No. 2,824,829, dated February 25, 1958. This black chrome-vanadium plating can be applied generally as outlined in detail in the aforementioned Patent No. 2,885,-

587. Briefly, this plating 36 is formed of chromium, vanadium and oxygen in which there are from 100 to 9.5 parts by weight of total chromium per part by weight of vanadium with the vanadium in the plating essentially compounded'as vanadium trioxide. The chromium in the plating is partially oxidized with the ratio of total chromium atoms to total oxygen atoms combined with chro- 'mium in the plating being from 2:1 to 100:1. The thickness of the blackchrome-vanadium plating is not critical although the exterior'surface of the shield should be "completely covered. As an example, the coating can have a thickness of about 0.05 mil. The surfaces of the plating adjacent the base metal forming theshields may tend to interact slightly with the base metal to form a complex compound, but the bulk of the plating including all exposed portions remains unreacted with the base metal. In order to realize any appreciable improvement in maintenance of light emission from such high-loaded discharge lamps, it is necessary that the heat shields 28 are provided with the foregoing plating 36 as specified. For best results, however, it is desirable that the portions of the lead conductors 22 which extend inwardly from the press and the enlarged anodes 26 also carry the foregoing black chrome-vanadium plating.

The maintenance of light output of controllamps using bare or unplated shields was compared to otherwiseidentical .lamps which incorporated the specified black chrome-vanadiumplating. After 2500 hours of operation, the control lamps "displayed a light output which was approximately 8.3% Of the light output measured at 100 hours operation. After 500 hours operation, the

.lamps incorporating the present black chrome-vanadium plating on the shields, lead conductors and enlarged anodes displayeda light output which was approximately 88% of the light output 'asmeasured at 100 hours operation. 'For a lamp as specified hereinbefore which is oper- 'ated with a .power input of approximately 100 watts, this represents after 500 hours operation an increase in output of about 400.1umens. It should be noted that the so-called initial output of fluorescent lamps is normally measured at '100 hours operation, at which time small variances encountered fromlamp to lamp will have substantially stabilized.

The foregoing performance figures are given for highlyloaded fluorescent lamps which incorporate a black chrome-vanadium plating 'on the anodes and lead condoctors as well as the shields. The plating may be omitted from either the anodes or lead conductors or .both, ifdesired. Where only the shields carrythis plat ing material, the improvement in maintenanceof light output will be decreased slightly, but will still bec'onsiderably better than .the control lamps. As noted hereinbefore, however, in order to realize any appreciable improvement over'the control lamps, it is necessary that the shields 28 carry the specified plating 36. The explanation for this improvement in maintenance of light output is not understood. In aforementioned Patent No. 2,885,587 it is'disclosed that a similar black chromevanadium coating on the inwardly-extending lead conductor portions of a standard 40-watt lamp will inhibit the first appearance of'end blackening. Such a coating as used on the lamp lead conductors, however, does not affect in any way the maintenance of light output for the usual fluorescent lamp, at least in any detectable amount. In addition, the heatshiel'ds ,28 operate at a relativelylow temperature thereby minimizing any effects of greater thermal emissivity realized with the specified coating 36. While the mechanism of operation by whichmaintenan'ce of light'output 'is'improved isnot understood, his clear that the maintenance of light output for the high-loaded fluorescent lamp's'which'utilize heat shields c'arryingthis specified plating is considerably improved.

It will be recognized that the objects of the invention have been achievedby providing a discharge device which is adapted 'to be operated with very high loadings and which has improved maintenance. In addition, there has been provided such a discharge device which incorporates lead conductors and enlarged anodes which also carry a specified plating material.

While best-known embodiments have been illustrated and described in detail, it is to beparticularly understood that the invention is not limited thereto or thereby.

I claim:

1. A mercury-vapor discharge device adapted to be operated under'such conditions as "would normally cause the operating mercury-vapor pressure within the device to exceed the pressure desired, said device comprising an elongated envelope, aphosphor coating on the interior surface of said envelope, an inert ionizable starting gas and a small charge of mercury contained within said envelope, lead-in conductors sealed through either end of and extending within said envelope, operativcly-disposedelectrodes electrically connecting to and supported by said lead conductors a short distance from either said electrodes, and 'a'black chromium-vanadium plating on said heat shields, said plating principally comprising from to"9.'5 parts by'weight of total chromium'per part by-weight of vanadium, the vanadium in said platingessentially compounded as V 0 and the chromium in said'plating'partially oxidized with the ratio of total chromium atoms to total oxygen atoms combined with chromium in said plating being from 2:1'to 100:1.

2. A mercury-vapor discharge device adapted to be operated under such conditions as wouldnormally the operating mercury vapor'pressure within the "device to exceed the pressure desired, said device comprising -an'elongatedenvelope, a phosphorcoating on the interior surface of said envelope, an inert ionizable starting gas and a small charge of mercury contained within said envelope, lead-in conductors sealed through either end of and extendingwithin said envelope, operatively-disposed electrodes electrically connecting to and supported by said lead conductors a short distance from either end of said envelope, enlarged anodes positioned proximate said electrodes and electrically connecting to said lead conductors, metallic heat-deflecting shields proxi- 'mate each end of said envelope and positioned closer to the ends of said envelope than said electrodes to form cooling chambers, each of said shields electrically connecting to one of the lead conductors supporting each of said electrodes, and a black chromium-vanadium plating on said heat shields and the portions of said lead conductors extending within said envelope, said plating principally comprising from 100 to 9.5 parts by weight of total chromium per part by weight of vanadium, the vanadium in said plating esesntially compounded as V 0 and the chromium in said plating partially oxidizing with the ratio of total chromium atoms to total oxygen atoms combined with chromium in said plating being from 2:1 to 100:1.

3. A mercury-vapor discharge device adapted to be operated under such conditions as would normally cause the operating mercury vapor pressure within the device to exceed the pressure desired, said device comprising an elongated envelope, a phosphor coating on the interior surface of said envelope, an inert ionizable starting gas and a small charge of mercury contained within said envelope, lead-in conductors sealed through either end of said envelope, operatively-disposed electrodes electrically connecting to and supported by said lead conductors a short distance from either end of said envelope, enlarged anodes positioned proximate said electrodes and electrically connecting to said lead conductors, metallic heatdefiecting shields proximate each end of said envelope and positioned closer'to the ends of said envelope than said electrodes to form cooling chambers, each of said shields electrically connecting to one of the lead conductors supporting each of said electrodes, and a black chromium-vanadium plating on said heat shields and said enlarged anodes, said plating principally comprising from to 9.5 parts by weight of total chromium per part by weight of vanadium, the vanadium in said plating essentially compounded as V 0 and the chromium in said plating partially oxidized with the ratio of total chromium atoms to total oxygen atoms combined with chromium in said plating being from 2:1 to 100:1.

'4. A mercury-vapor discharge device adapted to be operated under such conditions as would normally cause the operating mercury vapor pressure within the device to exceed the pressure desired, said device comprising an elongated envelope, a phosphor coating on the interior surface of said envelope, an inert ionizable starting gas and a small charge of mercury contained within said envelope, lead-in conductors sealed through either end of and extending within said envelope, operatively-disposed electrodes electrically connecting to and supported by said I lead conductors a short distance from either end of said envelope, enlarged anodes positioned proximate said electrodes and electrically connecting to said lead conductors, metallic heat-deflecting shields proximate each end of said envelope and positioned closer to the ends of said envelope than said electrodes to form cooling chambers, each of said shields electrically connecting to one of the lead conductors supporting each of said electrodes, and a black chromium-vanadium plating on said heat shields, the portions of said lead conductors extending within said envelope and said enlarged anodes, said plating principally comprising from 100 to 9.5 parts by weight of total chromium per part by weight of vanadium, the vanadium in said plating essentially compounded as V 0 and the chromium in said plating partially oxidized 1 with the ratio of total chromium atoms to total oxygen atoms combined with chromium in said plating being from 2:1 to 100:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,182,732 Meyer Dec. 5, 1939 2,433,404 Smith Dec. 30, 1947 2,692,350 Arnott Oct. 19, 1954 

